Helicoidal propeller and method of producing the same.



P. PAVATA.

HELIGOIDAL PROPELLBB AND METHOD or rnonuomc THE sun.

APPLICATION FILED D160. 28, 1909.

2 SHEETS-SHEET 1.

WITNESSES:

A MIA" 00.. MIN. D. l-

P. FAVATA. HELIGOIDAL PROPELLEB AND METHOD OF PRODUCING THE BLUE.

APPLICATION FILED DBO. 28, 1909.

1,034,773. Patented Aug. 6, 1912.

2 BESBTHHBE'! 2.

f4 j I I WITNESSES: INVENTOR:

WMWmVWI-t.

UNITED STATES PATENT OFFICE.

FRANCESCO FAVATA, OF LONDON, ENGLAND, ASSIGNOR T0 EDGAR COHEN, OF LONDON, ENGLAND.

HELICOIDAL PROPELLER AND METHOD OF PRODUCING THE SAME.

To all whom it may concern:

Be it known that I, F RANCESCO FAVATA, of 15 and 16 Cockspur street, London, England, engineer, have invented certain Improvements in Helicoidal Propellers and Methods of Producing the Same, of which the following is a specification.

The object of the present invention is to provide a helicoidal propeller or screw adapted to obviate disadvantages connected with the action of existing screw propellers, to increase the efiiciency of propulsion or thrust, and to reduce the resistances which, with ordinary propellers, absorb a lar e amount of motive ower and reduce efficiency. With this 0 ject I have devised a propeller or screw having a novel type of helicoidal surface which surface imparts to the propeller or screw special and characteristic properties. This new helicoidal surface is derived from a double-helicoidal surface which ma be generated by a straight line, a curved ine, or a combined straight and curved line, accordin to the particular obect to be attained. T1e surface is generated y the rotation of this generatrix about an axis which generatrix at the same time moves along said axis while at the sametime said eneratrix is applied constantly upon a gui in line contalned in a plane perpendicular or more or less inclined relatively) to the plane of the axis upon which the generatrix rotates. In this way a double helicoidal surface is traced out, the generating line being guided by the guide line and rotating about its axis or center of rotation, at the same time moving along its axis or line of displacement. The movement of the generatrix along its axis or line of displacement traces what I call the itch of origin and the direction of pitch 0 this pitch of origin is in the op osite direction to the pitch of the part of t e helicoidal surface on the outside of the guide line, which surface forms the active surface of the propeller to be formed.

In order to illustrate the manner in which the surface is generated,reference will be had to the accompanying drawings, wherem Figures 1 and 2 illustrate dia ammatically a develo ment of the lines 0 one blade of my prope er, Fig. 2 being a rojection of F1 1 in a plane perpendicu ar thereto, and Figs. 3 and 4 illustrate diagrammati Specification of Letters Patent.

Application filed December 28, 1909.

Patented Aug. 6, 1912.

Serial No. 535,325.

cally a development according to the plan of Figs. 1 and 2 of a two-blade propeller, Fig. at bein a projection of Fig. 3 in a plane perpendicu ar thereto.

I will assume by wa of example that the generating line or ra ius is a straight line H, Fig. 1 of the accompanying drawings, that the guide line, or line of application, is a parabola YOAG, and that the center 0 of the generating radius moves in a straight line OX perpendicular to the plane of the paper, Fig. 1 and perpendicular to the plane of the guide line, that is to say to the plane of the parabola YOAG. The generating radius OH is first applied at two points of the guide-line or parabola, say 0 and G. Consequentlfy this radius now coincides with the plane 0 the parabola or of the guide line. The foot 0 of the axis or line OX always coincides with the center of the generating radius at the commencement of its movement. The foot O of the axis or line OX might be at any point outside or upon the guide line, and the axis or line of displacement OX might be any line whatever, even a helicoidal line, according to the object in view. From the center 0 there is taken on the line OX a section OZ, which is the particular pitch of origin of the helicoidal surface considered. The helicoidal surface is now enerated with the generating radius OI? as follows :-The generating radius is moved around the axis or center 0 in the direction of the arrow WV for example, and at the same time the generating radius is moved along the axis or line of displacement OX keeping the generating radius always applied to the guide line YOAG the rate of movement of the generating radius on the guide line being preferably proportional to its rate of movement on its pitch of ori in. By takin successive positions, OH, I, OL, oM, 01$, or, oo, of the generating radius, which are represented in projection in Fig. 2 by OH, RI, SL, TM, UN, VP, ZQ, I obtain the above mentioned double helicoidal surface, with a pitch of origin OZ (Fig. 2) opposite in direction to the pitch of the part of the helicoidal surface AQHG, (Fig. 1) forming the active surface of the prope ler to be formed and which has an angular development determined b the angle formed by the two positions O OQ, of the generatin radius.

It will be seen that the helicoida surface as a whole has two developments contrary and inverse in a plane per endicular to the plane of the guide line AOG, that is to say the portion of the surface upon one side of the guide line YAOG has a helicoidal development inverse to the portion of the helicoidal surface located on the other side of said guide line. It will further be observed that for any position of the generating radius, for example the position ()AQ, (Fig. l) which is represented in projection by ZAQ in Fig. 2, the pitch of the surface ()ZAG varies gradually from OZ and diminishes to zero at the point where the gencrating radius coincides with the plane of the guide line and which in Fig. 2 corres )cnds to the point A; but that on the other side of the plane of the guide line it starts from zero and increases progressively along the generating radius from this point of contact A outward. Consequently the pitch of the exterior helicoidal surface increases progressively outwardly along the generating radius. Finally it will be observed that the pitch of the helicoidal surface AQHG increases progressively with the angular displacement of the generating radius, for during this movement the center of the radius moves out of the plane of the guide line along its axis. It will be seen therefore that the pitch of the helicoidal surface considered (AQHG) increases in all directions. In order to apply this new type of surface to the construction of helicoidal propellers for marine and aerial navigation for example, it is only necessary to take a segment of the helicoidal surface AQHG.

Referring to Fig. 3 it will be seen that a propeller blade or wing is here re resented by the segment of the helicoida surface AQHG, where the point A is the extreme point of the blade corresponding to the center of rotation of the propeller. This center does not, however, correspond to the center of origin of the helicoidal surface, which point is the point 0. The generating radius 0Q is diminished by the portion of the line comprised between the generating center 0 and the point of application of the generating radius on the guide line In a rt eller constructed in accordance with tie present plan the edge of the propeller corresponding to the generating radius 0Q may be tangential to the external circumfe ence f the boss. By thus displacin the oint of origin relatively to the point whlch is to be the axis of the propeller and reducin the absolute generating radius of the helicoidal surface to that portion which lies beyond the point of contact of the generating radius with the guide line, it is possible to obtain a smaller radius for the blade of the propeller and to secure the advantage of providing an entirely active thrust surface and of eliminating the central portion of the blade which in the known construction produces a vortex or eddy which increases the resistance and reduces efficiency. This decentralizing allows of constructing a propeller with a very small boss, leaving the entire helicoidal surface active. It also allows of obtaining an area of thrust greater than the area resulting from the radius of the blade. ()wing to the axis of the propeller or screw not coinciding with the center of the generating radius the vortex created by the propeller acting in its medium is not formed at the center of the propeller but at the center of the generating radius 0.

Owing to the principle on which it is constructed the helicoidal surface AQHG hereinhefore described has a pitch which increases progressively in all directions from r the origin. This secures the advantage that the propeller blades always have a complete active grip of the medium in which they work and are also enabled to utilize, for the efiiciency of the propeller, the lateral velocity of the said medium produced by the centrifugal force due to the motion of the propeller. Such progressively increasing inclination of the helicoidal surface has moreover the advantage of avoiding rarefaction of the medium on the thrust face of the blade. Each blade or wing possesses its own center of action upon the medium while existing propellers have only one center, the center of the propeller itse Eaoh center of action of the blades or wings of the present invention corresponds to the center of the absolute generating radius of the blade itself.

The extreme contour or outer edge HILMNPQ of the blade is determined according to the speed at which the propeller is intended to work, the medium in which it is to run, and so forth. In Fig. 3, the external contour is parabolic and Fig. 4 is its projection looking at it in a plane perpendicular to the plane of Fig. 3.

\Vhat I claim and desire to secure by Letters Patent is 1. A helicoidal propeller or screw, comprising a helicoidal surface having a pitch which increases in all directions from the origin and having a pitch of origin in a direction op osite to its pitch.

2. A he icoidal ropeller or screw, comprising a helicoidal surface having a pitch which increases in all directions from the origin and having a pitch of origin in a direction opposite to its pitch, each blade having its own center of action.

3. A helicoidal ropeller or screw, comprising a. helicoidal surface having a pitch which increases in all directions from the origin, and having a pitch of ori in in a direction opposite to its pitch, sai surface being the outer portion of a double helicoidal surface generated by the rotation of a generatin line around and along an axis or line of displacement, this generatrix being at the same time applied constantly upon a guiding line contained in a plane perpendicular or inclined relatively to a plane of the axis upon which the generatrix rotates, substantially as described.

4. A helicoidal ropeller or screw, comprising a helicoida surface having a pitch which increases in all directions from the origin, and having a pitch of origin in a direction opposite to its pitch, said surface being the outer portion of a double helicoidal surface obtained by the rotation of a line about a point moving in a line in a plane perpendicular or inclined to the plane of a uiding line to which latter the generatrix is constantly applied during its rotation.

5. In a helicoidal propeller or screw a blade or wing having a helicoidal surface the pitch of which increases in all directions from the origin and having a pitch of origin in a direction opposite to its pitch said helicoidal surface being displaced relatively to the axis of the propeller or screw substanti ally as and for the pur oses described.

6. In a helicoidal propeller or screw a blade or win having a helicoidal surface the pitch of w ich increases in all directions from the origin and havin a pitch of origin in a direction opposite to its pitch said helicoidal surface being displaced relatively to the axis of the propeller or screw and each blade or wing having its own center of action.

7. In a helicoidal propeller or screw a blade or win having a helicoidal surface the pitch of w ich increases in all directions from the origin and having a pitch of origin in a direction opposite to its itch, said surface being the outer portion 0 a double helicoidal surface generated by the rotation of a generating line around and along an axis or line of displacement, this generatrix being at the same time ap lied constantly upon a guiding line contalned in a plane perpendicular or inclined relatively to the plane of the axis u on which the generatrix rotates, and said elicoidal surface being displaced relativelv to the axis of the propeller or screw, substantially as and for the purposes described.

In witness whereof, I have hereunto signed my name in the presence of two subscribing witnesses.

FRANCESCO FAVATA.

Witnesses:

D. ROBERTO on SIMONE, HENRY ALLEN PRYER.

Copies of this patent may be obtained for flve cents each, by addressing the Commissioner of Patents, Washington, D. G. 

